org.reactfx.value.SimpleVar Maven / Gradle / Ivy

Go to download
package org.reactfx.value;

import java.util.Objects;

import javafx.beans.InvalidationListener;
import javafx.beans.value.ObservableValue;

import org.reactfx.Subscription;

class SimpleVar extends ValBase implements Var {
    private final InvalidationListener boundToListener = obs -> invalidate();

    private T value;
    private ObservableValue boundTo = null;

    public SimpleVar(T initialValue) {
        this.value = initialValue;
    }

    @Override
    public void bind(ObservableValue other) {
        if(other == null) {
            throw new IllegalArgumentException("Cannot bind to null");
        }

        if(boundTo != null) {
            boundTo.removeListener(boundToListener);
        }

        boundTo = other;

        if(isObservingInputs()) {
            boundTo.addListener(boundToListener);
        }

        invalidate();
    }

    @Override
    public void unbind() {
        if(boundTo != null) {
            boundTo.removeListener(boundToListener);
            boundTo = null;
        }
    }

    @Override
    public boolean isBound() {
        return boundTo != null;
    }

    @Override
    public void setValue(T value) {
        if(isBound()) {
            throw new IllegalStateException("Cannot set a bound property");
        } else {
            if(!Objects.equals(value, this.value)) {
                this.value = value;
                invalidate();
            }
        }
    }

    @Override
    protected Subscription connect() {
        if(boundTo != null) {
            boundTo.addListener(boundToListener);
        }

        return () -> {
            if(boundTo != null) {
                boundTo.removeListener(boundToListener);
            }
        };
    }

    @Override
    protected T computeValue() {
        if(isBound()) {
            value = boundTo.getValue();
        }
        return value;
    }
}